The primary role of the immune system is to protect against antigens derived from invading pathogens while recognizing and maintaining a tolerance to self-antigens. The recognition of self-antigens and maintenance of self-tolerance is facilitated by an intricate network involving effector T cells, helper T cells and (immuno)regulatory T cells.
Active immunization and activation of T cell-mediated immune response can be achieved through the administration of antigenic material or vaccines. Vaccines seek to prevent or ameliorate the harmful effects of many pathogens, and regular vaccination has become an integral part of preventive medicine. The principle of vaccination and immunization for disease prevention depends greatly on the immunological memory that is carried by memory B and T cells and that confers the ability to mount a rapid and strong immune responses to subsequent encounters with pathogens.
The ability of the immune system to respond to active vaccination with the buildup of a protective immunological memory progressively declines, however, with increasing age, rendering the elderly particularly vulnerable to infections, autoimmune diseases and neoplastic diseases. Although the elderly are considered at risk of complications of influenza and annual influenza vaccinations are strongly recommended by the World Health Organization for this population group, currently only 20% of elderly respond to such vaccinations with a sufficiently strong, protective immune response, while the remaining 80% remain vulnerable to infections with influenza virus. Age is a confounding factor in vaccine responses not only in the elderly, but already in the middle-aged adult. The decline is only partially explained by a loss of naïve and central memory CD4 T cells due to thymic involution. The present invention addresses this issue.